ABS molding materials having a bimodal rubber particle size distribution

Abstract

Rubber-modified, impact-resistant molding materials contain, based on the sum of A, B1 and B2, A: from 70 to 98% by weight of a polymer matrix A formed by free radical polymerization of a mixture of from 60 to 90% by weight of styrene and from 10 to 40% by weight of acrylonitrile, B1: from 1 to 29% by weight of a particulate, first graft copolymer B1 which is distributed in the matrix A and consists of a grafting base of polybutadiene and grafts of a copolymer of styrene and acrylonitrile having a mean particle size of about 100-500 nm, and B2: from 1 to 29% by weight of a particulate, second graft copolymer B2 distributed in the matrix A and consisting of a grafting base of polybutadiene and grafts of a copolymer of styrene and acrylonitrile having a mean particle size of from 600 to 10,000 nm, as obtained if both graft copolymers have been prepared by solution and/or mass polymerization and have been incorporated in the polymer matrix in a conventional manner.

We claim: 
     
       1. A process for the preparation of a rubber-modified, impact-resistant molding material containing from 70 to 98% by weight of a polymer matrix A, from 1 to 29% by weight of a particulate, first graft copolymer B1, and from 1-29% by weight of a particulate, second graft copolymer B2, which process comprises (1) preparing component A by free radical polymerization of a mixture of 60 to 90% by weight of styrene and from 10 to 40% by weight of acrylonitrile; (2) preparing component B1, which consists of a grafting base of polybutadiene and grafts of a copolymer of styrene and acrylonitrile having a mean particulate size of about 100-500 nm, by solution polymerization; (3) preparing component B2, which consists of grafting base of polybutadiene and grafts of a copolymer of styrene and acrylonitrile, having a mean particulate size of from 600 to 10,000 nm, by solution polymerization; and (4) mixing components A, B1 and B2 in the form of granules and are melted together.